S. Arunkumar

Artificial neural network-based temperature prediction in heat sinks with cross cuts fins

Soft computing techniques are predominantly used in varied sectors of research for accurate prediction and optimisation. Recent advancements in artificial neural network ANN and its capability to predict the data have increased its range of applications including heat transfer problems. The present paper aims to predict base plate temperature of cross cut fins of variable height 5-15 mm, fin spacing 5.85-32 mm, number of crosscuts 0-5, heat duty 20-100 W for constant fin thickness 3 mm and base plate dimensions 180 × 250 mm. A neural network model is designed for a rectangular heat sink with cross cut fins. The model is developed using the data from numerical heat transfer calculation carried out in ANSYS FLUENT©. The numerical model is validated with similar experimental results available in literature. The simulated data are used to train several neural-network configurations and the best neural-network model is used for prediction. The ANN model is used to predict the base plate temperatures of cross cut fins. The results reveal the ability of using ANN for accurate prediction of base plate temperature.

Design of motor speed control using LabVIEW for air-flow control in wind tunnels

Wind tunnels are used in aerodynamic and heat transfer research to analyze various effects on solid objects when air is forced on to them. This is done using a powerful fan or by a blower. These wind tunnels are equipped with suitable sensors for sensing various parameters like pressure variation, calculating the aerodynamic forces and other fluid flow characteristics. In present work, velocity of air in wind tunnel is controlled by adjusting the fan speed. The fan speed is controlled by varying the voltage supplied to the motor using DAC0808. DAC0808 converts the digital value to analog voltage. The digital value is obtained by considering the set point given (required RPM) by the user through LabVIEW graphical interface. This work describes in detail the user interface developed in LabVIEW that can be used in applications where variable speed required can be attained using a GUI based control.

Automated temperature control in batch reactor using LabVIEW

Maintaining the temperature of a batch reactor is essential in many chemical and manufacturing processes such as batch distillation, chemical mixing and polymerisation. There is a requirement to control the speed of stirrer in an exothermic chemical mixing reaction to ensure an optimal stirring and to maintain the temperature of the reactor under control. Temperature of reactor can also be maintained by controlling the flow of liquid through valves. In this paper an effort is made to control the opening and closing of the valves and speed of stirrer using stepper motor. The control action is taken based on the reactor temperature and desired temperature (set point) given through LabVIEW graphical user interface. The present work is focused on providing an user friendly interface in LabVIEW to achieve a software based control for stepper motor using 8051 microcontroller, which can be used in the applications where valve and speed control and is required based on temperature.

Application of image processing for a bubble column reactor

Two phase flow is the simultaneous flow of two phases predominantly a gas and a liquid. A bubble column reactor is an example of the application of two phase flows. Bubble column reactors find their use in bioprocesses and in chemical industries. In this article the changes in the nature of air bubbles due to the change in flow rate has been studied using image processing techniques. The flow rate of air is controlled by a flow control valve. Photographs of the bubbles are taken for various velocities. An Image processing algorithm is developed using various image processing techniques and the photographs are analysed. The properties such as the velocity, shape and area of the bubbles are studied by image processing techniques.

Determination of Two Phase Flow Slug Velocity and Length Using Infrared Sensor

The concurrent flow of two different liquid or gaseous phases is termed as two phase flow. The study of two phase flow is important due to its wide applications in industries. Its applications include cooling, refrigeration, atomization of fuels, chemical processing and cryogenics. Study of two phase flow parameters such as velocity and length of two phase slug flow pattern is significant in analyzing the heat transfer characteristics in the case of refrigeration and chemical process industries. In the present study, a pair of infrared emitter and receivers is used to determine the velocity and the length of a slug type two phase flow. By knowing the distance between the IR pairs and by calculating the time taken using a DAQ, velocity and length can be determined. Image processing and high speed videography technique is used to validate the obtained results.

Computational Modeling and Analysis of Fluid Structure Interaction in Micromixers with Deformable Baffle

Abstract A passive micromixer with obstacles in the form of deformable baffles is examined numerically. The model deploys an Arbitrary Lagrangian-Eulerian framework with Fluid-structure interaction coupled with a diffusion–advection model. Numerical analysis is carried out in the Reynolds number [Re] range of 0.01≤Re≤300. The objective of the present study is to enhance mixing between two component flow streams in a microchannel encompassing a deformable baffle. In the present work, the baffle deforms only due to the dynamic force of fluids. No external forces are applied. To exemplify the effectiveness of the present design, water and a suspension of curcumin drug loaded nanoparticles are taken as two fluids. Mixing index based on the variance of the local concentration of the suspension is employed to appraise the mixing performance of the micromixer. The introduction of the deformable baffle in a micromixer proliferates the mixing performance with minimal pressure drop over the tested Reynolds number range.

Laser-Based Measurement of Gas–Liquid Two-Phase Flows in Micro and Mini Channels using Multiple Photodiode Arrangement

Two-phase flow measurement is important in process and chemical industries. In the present work, a measurement technique for the characterization of two-phase flows using a laser and an arrangement of the photodiodes is proposed and tested. Two-phase flow experiments were carried out in 1.80, 3.14, and 4.68-mm-diameter glass tubes. A high-speed camera was used to analyze the various optical patterns formed by a stationary laser beam on a screen during bubbly, slug, and stratified flows, which have been discussed in detail in Navisa et al. (2015). Photodiodes are arranged on the screen based on high-speed camera recordings. A procedure is demonstrated to calculate the flow regime velocity and length based on the photodiode outputs. The designed nonintrusive instrumentation determines the two-phase flow parameters in real time for flow in optically transparent mini channels. The accuracy of the measurement technique and the limitations are also discussed.

Hydrodynamic Study of Bubbles in a Bubble Column Reactor Part II – Numerical Study

The present work deals with the use of CFD analysis and the validation of the experimental work carried out on the artificial splitting of an air bubble in a bubble column reactor. In Part I of this work, artificial splitting of bubble in a bubble column rector is experimentally studied by using a high speed camera. Image processing technique was used to identify bubble size and bubble velocity. In present work CFD simulations are carried out using ANSYS FLUENT software using Volume of Fluids (VOF) method. VOF is based on a surface tracking technique applied to a fixed Eulerian space. The phase fraction in physical quantities that can be used to distinguish the distribution of gas hold up in a bubble Column reactor. The numerical study of splitting of bubble into two bubbles of nearly equal size is considered. In the bubble column reactor, the liquid phase is stationary and gas flow rate in it is varied. The superficial gas flow rates are 10 lph, 15 lph, 20 lph and 25 lph. The characteristics of bubble after splitting which include its shape, size and velocity for various gas flow rates mentioned above are studied numerically and are compared with experimental results. These hydrodynamic characteristics play a pivotal role in the reactions occurring between the liquid and gas phases in the bubble column reactor.

Investigation of Single Water Droplet Evaporation over Aluminium Surfaces Using High Speed Camera and Image Processing

The study of evaporation of water droplets over horizontal heated surfaces is an intense area of research because of its wide application in various fields of heat transfer. The characterization of the behavior of water droplets is important in studying the cooling effects produced over impinging surfaces. The present study focuses on analyzing the shape and size of the droplets by applying image processing techniques. In the present work, a fixed volume of single water droplet is made to impinge on a horizontal Aluminium surface using a designed microcontroller based syringe pump. The formation and the dynamics of bubbles are recorded using a high speed camera. Image processing technique is used to determine the droplet parameters such as contact angle, spreading radius and to study the shape of the droplet. The surface temperature is measured using a Thermocouple connected to an online Data acquisition system. The effect of the characteristics of droplet on the decrease in surface temperature can be seen from the temperature – time graph and the processed photographs taken using high speed camera. The decrease in base plate temperature is found to be depending on the behavior and the properties of the droplet.

Numerical Studies on Natural Convection Heat Transfer – Fins with Closed Top

Fins are extended surfaces provided to enhance the heat transfer rate of a system. Several attempts have been made in the past to augment the heat transfer rate by using fins of various geometries. In the present study an array of rectangular fins with closed top, standing on a vertical base is analysed under natural convection conditions using commercial CFD code ANSYS FLUENT©. The numerical model is validated with the available experimental results for fins with open top under natural convection conditions. The plate fin heat sink is analysed for a constant heat duty of 60 W. The height, thickness and length of the fins are taken to be constant throughout the analysis. A detailed study is carried out to examine the dependency of the base plate temperature on the thickness of the closed top and on the number of fins. It is concluded based on the analysis that heat fins with closed top are found to have a decreased base plate temperature compared to the conventional rectangular fins.